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• Hydrometeorological Hazards


  Dangers associated with the natural processes or phenomena involved in the transfer of water and energy between the land surface and the lower atmosphere
• The geographic location of the Philippines does not only pose geological threats but also hydrometeorological hazards
• The Philippines is in the Northern Hemisphere, which is above the equator. The area near the equator, known as the Intertropical Convergence Zone (ITCZ), is where trade winds meet
• Trade winds flow in opposite directions and this is the reason that strong swirling of wind happens
• As a result of this swirling movement, frequent natural hazard hazards in the atmosphere and oceans take place
• Hydrometeorological Hazards


  • Typhoons
  • Thunderstorms
  • Flash floods
  • Floods
  • Storm surges
  • Tornadoes
  • El Nino
  • La Nina
• Typhoon


  Intense circulating winds with heavy rain over tropical waters and land
• Formation of tropical cyclones in the Philippines

  1. Warm surface of Pacific Ocean

  2. Increase in temperature and humidity

  3. Trade winds spiral

  4. Cyclone strengthens as it moves westward
• Tropical cyclone classifications


  • Tropical depression (up to 61 kph)
  • Tropical storm (62 to 88 kph)
  • Severe tropical storm (89 to 117 kph)
  • Typhoon (118 to 220 kph)
  • Super typhoon (exceeding 220 kph)
• Typhoons usually lose their energy when they make landfall due to the large mass of land, especially terrains characterized by mountains and slopes, which breaks up the pressure of the cyclone
• Typhoons also weaken when they enter a cooler and drier environment because they come from warm, moist tropical air
• Public Storm Warning Signal #1


  Winds 30-60 kph, wave height 1.25-4.0 meters, very light or no damage to high risk structures, light to medium and low risk structures, slight damage to some houses of very light materials or makeshift structures in exposed communities, some banana plants tilted, a few downed and leaves generally damaged, twigs of small trees may be broken, rice crops may suffer significant damage when in flowering stage
• Public Storm Warning Signal #2


  Winds 61-120 kph, wave height 4.1-14.0 m, storm surge possible, light to moderate damage to high risk structures, very light to light damage to medium-risk structures, no damage to very light damage to low risk structures, unshielded, old dilapidated schoolhouses, makeshift shanties, and other structures of light materials partially damaged or unroofed, some old galvanized iron (G.I.) roofs may be peeled or blown off, some wooden, old electric posts tilted or downed, some damage to poorly constructed signs/billboards, most banana plants, a few mango trees, ipil-ipil and similar trees downed or broken, some coconut trees tilted with few others broken, rice and corn may be adversely affected, considerable damage to shrubbery and trees with some heavy-foliaged trees blown down
• Public Storm Warning Signal #3


  Winds 121-170 kph, wave height > 14.0 meters, storm surge possible, heavy damage to high–risk structures, moderate damage to medium-risk structures, light damage to low-risk structures, increasing damage to old, dilapidated residential structures and houses of light materials (up to 50% in a community), houses of medium strength materials (old, timber or mixed timber-CHB structures, usually with G.I. roofings), some warehouses or bodega-type structures unroofed, almost all banana plants downed, some big trees (acacia, mango, etc.) broken or uprooted, dwarf-type or hybrid coconut trees tilted or downed, considerable damage to shrubbery and trees with heavy foliage blown off, some large trees blown down
• Public Storm Warning Signal #4

  Winds 171-220 kph, wave height more than 14.0 meters, storm surge 2-3m possible, very heavy damage to high–risk structures, heavy damage to medium risk structures, moderate damage to low-risk structures, considerable damage to structures of light materials (up to 75% are totally and partially destroyed), complete roof structure failures, many houses of medium-built materials unroofed, some with collapsed walls, extensive damage to doors and windows, a few houses of first-class materials partially damaged, all signs/billboards blown down, almost total damage to banana plantation, most mango trees, ipil-ipil and similar types of large trees downed or broken, coconut plantation may suffer extensive damage, rice and corn plantations may suffer severe losses
• Public Storm Warning Signal #5

  Winds > 220 kph, wave height more than 14.0 m, storm surge more than 3 meters possible, widespread damage to high-risk structures, very heavy damage to medium-risk structures, heavy damage to low-risk structures, almost total damage to structures of light in highly exposed coastal areas, complete roof failure on many residences and industrial buildings, severe and extensive window and door damage, most residential and institutional buildings of mixed construction may be severely damaged, electrical power distribution and communication services severely disrupted, all signs/billboards blown, total damage to banana plantation, most tall trees broken, uprooted or defoliated, coconut trees stooped, broken or uprooted, few plants and trees survived
• Thunderstorm


  Storm characterized by heavy rain with the presence of thunder and lightning
• Formation of thunderstorms


  1. Uneven distribution of heat in the air and on land

  2. Heat from Earth's surface flows upward, cold air from atmosphere sinks

  3. Transfer of heat makes air unstable

  4. Rapid rising warm air with moisture causes thunderstorms
• Thunderstorms usually happen in summer because of the atmosphere's high humidity and high temperature
• Lightning formation in thunderstorms

  1. Collision of water droplets in clouds breaks away electrons

  2. Electrons gather in lower portion of clouds, upper portion becomes positively charged

  3. When clouds near ground pick up positively charged object, electric current produced

  4. Rapid expansion of air results in thunder
• Hazards associated with thunderstorms

  • Heavy rainfall leading to flooding
  • Lightning that can electrocute and damage electrical facilities
  • Air turbulence that can displace or disorient aircraft
  • Fire that can burn buildings and vegetation
• Flood


  Presence of excessive water on a supposedly dry land, caused by continuous heavy rain or poor drainage, low-lying areas prone to flooding
• Problems caused by flooding in densely populated areas

  • Disruption of commercial and industrial operations leading to loss of income
  • Stand-still traffic causing paralysis in network transportation and communication
  • Displacement of affected homes and families
  • Damaged properties resulting from corrosion and water intrusion
  • Waterborne diseases such as leptospirosis and typhoid fever
• Flash Flood


  Rapid flow of water on saturated or dry soil with poor absorption, usually on slopes like mountains, volcanoes, and waterways, caused by extensive rainfall or man-made structures like dam overflows
• Storm Surge


  Abnormal rise in coastal waters due to massive force from the sea or air above, strong winds of typhoons push sea waters toward shore, can instantly flood coastal areas and accumulate to flood low-lying inland areas, can be aggravated by high tide
• Tornado


  Rapidly rotating column of air in contact with air and land, can pick up and sling away objects
• An average of 12-24 tornadoes hit the Philippines every year, mostly occurring in flat terrains such as Mindanao and Central Luzon, especially Nueva Ecija and Bulacan
• Formation of tornadoes


  1. Strong winds and low thunderstorm clouds

  2. Turbulent clouds pushed to ground due to low pressure and strong winds

  3. Warm air on ground contacts thunderstorm clouds, creating cyclonic, counter-clockwise motion
• El Niño


  Large-scale warming of the ocean and atmosphere across the central and east-central Equatorial Pacific, causes warmer winters in Canada and western US, warmer cold season in Philippines
• La Niña


  Lower sea surface temperatures by 3-5 degrees Celsius in eastern Pacific, causes excessive rainfall and cold temperatures in Philippines
• Instruments used to monitor hydrometeorological hazards

  • Doppler radar
  • Automated rain gauge
• Doppler radar is used to measure weather parameters like rainfall amount, wind direction, speed and intensity to forecast weather and upcoming typhoons
• Automated rain gauges are installed in telecommunication cell sites to observe and locate areas with excessive rainfall, used to detect possible flooding and flash floods
• La Niña


  A climate pattern that occurs in the eastern part of the Pacific Ocean, characterized by lower sea surface temperatures by 3-5 degrees Celsius
• La Niña begins in the eastern part of the Pacific Ocean


  Similar to the location of El Niño
• During La Niña


  Cyclones formed shift westward going to the direction of China, affecting the Philippines with excessive rainfall and cold temperatures
• Tools for Monitoring Hydrometeorological Hazards

  • Doppler radar
  • Automated rain gauge
• Doppler radar


  Used to measure weather parameters like rainfall amount, wind direction, speed and intensity to forecast weather conditions and upcoming typhoons
• Automated rain gauge


  Installed in telecommunication cell sites to observe and locate areas with excessive rainfall, used to detect possible flooding and flash floods
• Most hydrometeorological hazards can be heard seconds before they reach your area, with rumbling sounds indicating the coming of a tornado, flash floods, and storm surges